The element gallium occurs naturally as 69- and 71-isotopes with the former making up 60% of the natural abundance. Both isotopes are used in semiconductor production. They are also the main ingredients for gallium arsenide crystals which make up the laser diodes in cell phones and other electronics.
Like many elements, gallium is toxic when ingested. However, it depends on dosage and circumstance. A dosage toxic to a guinea pig will be different from that of humans and even this varies depending on the environment. Generally, it is safe to touch but will stain everything it touches. It will also liquefy at temperatures just above the human skin temperature.
In chemistry, gallium is an odd metal that does not form strong bonds with most other metals. The exception is the noble metal tungsten which is joined with it in alloys. It also reacts with oxygen to form gallium oxide. Gallium is used in the manufacture of light-emitting diodes (LEDs) because of its ability to be turned on and off quickly. It is also used in specialized PET scans as a radioisotope.
The short-lived 68Ga isotope of gallium has an excellent clinical track record for use in bone imaging. It is produced in small quantities by the natural decay of the radioisotope germanium-68 in so-called Ge-68/Ga-68 generators and can be created in much greater quantities by proton bombardment of 68Zn in low-energy medical cyclotrons. It is commonly attached to a molecule such as the somatostatin analogue DOTATOC for use in a limited number of diagnostic PET scans.